traversal.hh

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// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
// SPDX-FileCopyrightInfo: Copyright © DUNE Project contributors, see file LICENSE.md in module root
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-GPL-2.0-only-with-PDELab-exception
 
#ifndef DUNE_TYPETREE_TRAVERSAL_HH
#define DUNE_TYPETREE_TRAVERSAL_HH
 
#include <utility>
 
#include <dune/common/hybridutilities.hh>
#include <dune/common/indices.hh>
#include <dune/common/std/type_traits.hh>
 
#include <dune/common/typetree/childaccess.hh>
#include <dune/common/typetree/nodeconcepts.hh>
#include <dune/common/typetree/traversal.hh>
 
#include <dune/typetree/treepath.hh>
#include <dune/typetree/visitor.hh>
 
namespace Dune {
  namespace TypeTree {
 
    namespace Detail {
 
      // SFINAE template check that Tree has a degree() function and a child() function accepting integer indices
      template<class Tree>
      using DynamicTraversalConcept = decltype((
        std::declval<Tree>().degree(),
        std::declval<Tree>().child(0u)
      ));
 
      // SFINAE template check that Tree has static (constexpr) function Tree::degree()
      template<class Tree>
      using StaticTraversalConcept = decltype((
        std::integral_constant<std::size_t, Tree::degree()>{}
      ));
 
 
      template<class Tree, TreePathType::Type pathType, class Prefix,
        std::enable_if_t<Tree::isLeaf, int> = 0>
      constexpr auto leafTreePathTuple(Prefix prefix)
      {
        return std::make_tuple(prefix);
      }
 
      template<class Tree, TreePathType::Type pathType, class Prefix,
        std::enable_if_t<not Tree::isLeaf, int> = 0>
      constexpr auto leafTreePathTuple(Prefix prefix);
 
      template<class Tree, TreePathType::Type pathType, class Prefix, std::size_t... indices,
        std::enable_if_t<(Tree::isComposite or (Tree::isPower and (pathType!=TreePathType::dynamic))), int> = 0>
      constexpr auto leafTreePathTuple(Prefix prefix, std::index_sequence<indices...>)
      {
        return std::tuple_cat(Detail::leafTreePathTuple<TypeTree::Child<Tree,indices>, pathType>(Dune::TypeTree::push_back(prefix, Dune::index_constant<indices>{}))...);
      }
 
      template<class Tree, TreePathType::Type pathType, class Prefix, std::size_t... indices,
        std::enable_if_t<(Tree::isPower and (pathType==TreePathType::dynamic)), int> = 0>
      constexpr auto leafTreePathTuple(Prefix prefix, std::index_sequence<indices...>)
      {
        return std::tuple_cat(Detail::leafTreePathTuple<TypeTree::Child<Tree,indices>, pathType>(Dune::TypeTree::push_back(prefix, indices))...);
      }
 
      template<class Tree, TreePathType::Type pathType, class Prefix,
        std::enable_if_t<not Tree::isLeaf, int>>
      constexpr auto leafTreePathTuple(Prefix prefix)
      {
        return Detail::leafTreePathTuple<Tree, pathType>(prefix, std::make_index_sequence<Tree::degree()>{});
      }
 
      /* The signature is the same as for the public applyToTree
       * function in Dune::Typetree, despite the additionally passed
       * treePath argument. The path passed here is associated to
       * the tree and the relative paths of the children (wrt. to tree)
       * are appended to this.  Hence the behavior of the public function
       * is resembled by passing an empty treePath.
       */
 
      /*
       * This is the overload for leaf traversal
       */
      template<class T, class TreePath, class V,
        std::enable_if_t<std::decay_t<T>::isLeaf, int> = 0>
      void applyToTree(T&& tree, TreePath treePath, V&& visitor)
      {
        visitor.leaf(tree, treePath);
      }
 
      /*
       * This is the general overload doing child traversal.
       */
      template<class T, class TreePath, class V,
        std::enable_if_t<not std::decay_t<T>::isLeaf, int> = 0>
      void applyToTree(T&& tree, TreePath treePath, V&& visitor)
      {
        using Tree = std::remove_reference_t<T>;
        using Visitor = std::remove_reference_t<V>;
        visitor.pre(tree, treePath);
 
        // the visitor may specify preferred dynamic traversal
        using preferDynamicTraversal = std::bool_constant<Visitor::treePathType == TreePathType::dynamic>;
 
        // create a dynamic or static index range
        auto indices = [&]{
          if constexpr(preferDynamicTraversal::value && Concept::UniformInnerTreeNode<Tree>)
            return Dune::range(std::size_t(tree.degree()));
          else
            return Dune::range(tree.degree());
        }();
 
        if constexpr(Concept::InnerTreeNode<Tree>) {
          Hybrid::forEach(indices, [&](auto i) {
            auto&& child = tree.child(i);
            using Child = std::decay_t<decltype(child)>;
 
            visitor.beforeChild(tree, child, treePath, i);
 
            // This requires that visitor.in(...) can always be instantiated,
            // even if there's a single child only.
            if (i>0)
              visitor.in(tree, treePath);
 
            constexpr bool visitChild = Visitor::template VisitChild<Tree,Child,TreePath>::value;
            if constexpr(visitChild) {
              auto childTreePath = Dune::TypeTree::push_back(treePath, i);
              applyToTree(child, childTreePath, visitor);
            }
 
            visitor.afterChild(tree, child, treePath, i);
          });
        }
        visitor.post(tree, treePath);
      }
 
    } // namespace Detail
 
 
    // ********************************************************************************
    // Public Interface
    // ********************************************************************************
 
    template<class Tree, TreePathType::Type pathType=TreePathType::dynamic>
    constexpr auto leafTreePathTuple()
    {
      return Detail::leafTreePathTuple<std::decay_t<Tree>, pathType>(hybridTreePath());
    }
 
 
    template<Concept::TreeNode Tree, typename Visitor>
    void applyToTree(Tree&& tree, Visitor&& visitor)
    {
      Detail::applyToTree(tree, hybridTreePath(), visitor);
    }
 
 
  } // namespace TypeTree
} //namespace Dune
 
#endif // DUNE_TYPETREE_TRAVERSAL_HH